In the molding of products, such as injection molding of plastic products, it is sometimes desirable to be able to provide such products with identifying indicia during the molding operation. In U.S. Pat. No. 4,254,933, there is disclosed an injection molding operation wherein a plurality of security seals are molded during each molding operation. The plurality of molded security seals are provided with identifying indicia and are produced without repetitions but numerical sequence. In U.S. Pat. No. 4,137,962, a movable member is located in a casting-marking apparatus which is adapted for incorporation in a permanent foundry pattern of the type used to produce sand molds for initial castings. The apparatus carries a marking that is impressed in the sand mold and subsequently reproduced on a casting. The marking is altered from a station remote from the pattern. The marking is used to mark castings with information that periodically changes such as the hour at which the casting is made.